Memory devices are typically provided as internal, semiconductor, integrated circuits in computers or other electronic devices. There are many different types of memory including random-access memory (RAM), read only memory (ROM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), and flash memory. One type of flash memory is a nitride read only memory (NROM). NROM has some of the characteristics of flash memory but does not require the special fabrication processes of flash memory. NROM integrated circuits can be implemented using a standard CMOS process.
Flash memory devices have developed into a popular source of non-volatile memory for a wide range of electronic applications. Flash memory devices typically use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption. Common uses for flash memory include personal computers, personal digital assistants (PDAs), digital cameras, and cellular telephones. Program code and system data such as a basic input/output system (BIOS) are typically stored in flash memory devices for use in personal computer systems.
As the size of memory devices shrinks, so too does the charge trapping capacity of those devices. And, as the charge trapping capacity shrinks, so does the threshold voltage difference that differentiates the programmed states of the device. Because variations in the operational characteristics of these ever-shrinking memory devices can have serious effects on the ability of the memory devices to perform reliably, it is important to enhance the charge trapping ability of these memory devices. In this way, the effect of variations in the operational characteristics of a memory device can be more easily accommodated and it will be possible to more reliably discriminate between the programmed states of the device. Accordingly, there is a need for an improved memory device having an enhanced charge trapping ability.